A known developer cartridge to be attached to an electrophotographic printer includes a casing in which toner is stored, a developing roller configured to carry toner on a surface thereof, and a layer-thickness regulating member configured to regulate toner carried on the surface of the developing roller to a predetermined thickness.
In the developer cartridge, the casing has an opening from which the developing roller is exposed. Before shipment or transportation, a developing roller cover is attached to the developer cartridge to cover the developing roller exposed from the opening, and then the developer cartridge is packaged in a shipping carton.
In addition, the need to reduce the physical size of the developer cartridge has been recently demanded. Thus, a developer cartridge in which a layer-thickness regulating member is disposed so as to be exposed from a casing has been proposed.
However, when the developer cartridge packaged as described above accidentally drops during shipment, the developing roller may be deformed due to drop impacts, resulting in that a gap may be formed between the developing roller and the layer-thickness regulating member. In this case, toner may leak from the gap between the developing roller and the layer-thickness regulating member.